Research Paper|Volume 12, Issue 21|pp 21355—21375

Association of folate intake and plasma folate level with the risk of breast cancer: a dose-response meta-analysis of observational studies

Xueting Ren^1,²^,*, Peng Xu^1,²^,*, Dai Zhang^1,²^,*, Kang Liu³, Dingli Song^1,², Yi Zheng², Si Yang², Na Li^1,², Qian Hao², Ying Wu², Zhen Zhai², Huafeng Kang²^,&, Zhijun Dai^1,²^,&

¹Department of Breast Surgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
²Department of Oncology, The Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
³Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China

* Equal contribution

& This corresponding author has a verified history of publications using a personal email address for correspondence.

Received: May 7, 2020Accepted: July 25, 2020Published: November 4, 2020

https://doi.org/10.18632/aging.103881

Copyright: © 2020 Ren et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

Epidemiological studies showing the correlation between folate and the breast cancer risk have revealed inconsistent results. Hence, we conducted a dose-response meta-analysis of observational studies to obtain more reliable conclusions. We searched PubMed and Embase for studies published before April 2019 and identified 39 studies on folate intake and 12 studies on plasma folate level. The combined odds ratios (ORs) and 95% confidence intervals (CIs) were extracted to estimate the breast cancer risk. Folate intake was inversely correlated with the breast cancer risk when the highest and lowest categories (OR = 0.85, 95% CI = 0.79–0.92) were compared, and the dose-response result showed that folate intake had a linear correlation with the breast cancer risk. Moreover, a higher folate intake correlated with a lower breast cancer risk in premenopausal women (OR = 0.80, 95% CI = 0.66–0.97), but not in postmenopausal women (OR = 0.94, 95% CI = 0.83–1.06). However, plasma folate levels were not correlated with the breast cancer risk (OR = 0.98, 95% CI = 0.82–1.17). Folate intake was negatively correlated with the breast cancer risk; however, its practical clinical significance requires further study. Furthermore, additional folate supplements should be considered carefully.